Shining light on excited-state dynamics in perovskite materials
Through a close collaboration between experimentalists at University of California Berkeley and theorists in Los Alamos's Theoretical Division group T-1, the Center for Nonlinear Studies (CNLS), and Center for Integrated Nanotechnology (CINT), researchers have performed femtosecond transient absorption and density functional theory simulations to probe the excited-state dynamics of hybrid perovskite MAPbI3 and found evidence for coherent skeletal vibration dynamics that lead to formation of a polaron state underscoring charge separation. The low-frequency wave packet modes are observed principally for the Pb-I bending and stretching vibrations resulting from the different geometry of the polaron state compared to the neutral state. The high efficiency of MAPbI3 perovskite solar cells may be yet another example of the importance of vibrational coherence in efficient photochemical dynamics.